Variable pressure hydraulic control circuit for fluid actuated rams



May 16, 1950 H. M. PURCELL 2,507,868

VARIABLE PRESSURE HYDRAULIC CONTROL CIRCUIT FOR FLUID ACTUATED RAMSFiled July 8, 1947 l r g. E.

65 L Sfarf Z Z :4 BZ 6:5!- m a INVENTOR. --o o- 5 I 62 HOWARD N. FUR asJZMfI "ZW ATTORA/f/J Patented May 16 1950 VARIABLE PRESSURE HYDRAULICCON- CIRCUIT FOR FLUID ACTUATED Howard M. Purcell, Philadelphia, Pa.,assignor to H-P-M Development Corporation, Wilmington, Del., acorporation of Delaware Application July 8, 1947, Serial No. 159,673

4 Claims.

1 This invention relates to hydraulic circuits, and particularly tohydraulic circuits employing fluid intensiflers or pressure connectorsof the type disclosed in the Warren R. Tucker applicain which thechange-over from one pressure to another is accomplished smoothly andautomatically. I

These and other objects and advantages will become more apparent uponreference to the 66 following description taken in connectionwith theaccompanying drawing in which:

Figure 1 is a diagrammatic view of a hydraulic operating circuitaccording to this invention; and

tion, Serial No. 594,413, filed May 18, 1945, now 5 Figure 2 is adiagrammatic electrical control Patent No. 2,486,079, and assigned tothe same circuit for controlling the valves of the circuit assignee asthe instant application. of Figure 1.

The fluid pressure convertor disclosed in the Referring to the drawingthere is showna aforementioned Tucker application is charactercylinderto within which is reciprocably mounted ifzed by its ability to passfluid in one direction the double acting ram l2 which defines with themm a fluid source at increased pressure and said cylinder the ramadvancing means l4 and reduced volume and, in the opposite direction atram retracting means I6. decreased pressure and increased volume. ThisThe pressure for operating the ram I2 is obis accomplished by modifyingthe volume of the tained from a pump l8 which is connected to fluidpassing through the converter by a condraw fluid from a reservoir andwhich disnection with exhaust which either diverts a porcharges the saidfluid to a conduit 22. Y tion of the supply of fluid to exhaust whileThe conduit 22 is connected by a conduit 24 utilizing the pressureenergy thereof for comwith two ports of a four-way valve 26 whichpressing the remainder of the fluid to a higher 20 has therein areciprocable valve member 28. The pressure or, adds to the supply offluid by fluid valve 26 also has a pair of ports connected retaken fromexhaust and distributes the pressure spectively by the conduits 30 and32 with two energy in the supply of fluid throughout the ports of afluid pressure intensifier or conductor en iiilrle volume tof thedlischai'rged fluid. b b 34 of ihleI tygellgsg lzgsed in ghgvgaggeri 1sconver or is a so c arac erized y eing Pa on or issue 0 s p rabl todischarge fluid to exhaust when bo h intensifier also has an exhaustport connected by the inlet and outlet of the converter are contheconduit 36 with the reservoir 20. nected w1th a source of fluid. Inoperation, when fluid is supplied to the i The irdistlaraiiilrlilvention clonfirriaidzwitlil a1; gnverggordiilli througth t3:COIldllt 303:, sulpplty of mprove y a 10 c1rcu1 w 10 u es a o uid evered o e con ui W ic is the of rae in apa i ies f t p s ure augmentedby additional fluid drawn in by the v r 1' and y doing 80 ighly use 111but y converter through the conduit 36 but at reduced simple hydraulicoperating circuit results. This pressure, conversely, wh n fluid issupplied to circuit is adapted for machine tool installations, theconvertor 34 by the conduit 32 there is a hydraulic pressing Opera a dfor other aD- supply of fluid to the conduit 30 from the conp ggguz gugz g g gg s zg gg jgg pgg f vertor 34 which is reduced in volume by apredetermined amount of fluid which is by-passedpresen invention toprovide n m d but from the convertor through the conduit 35 to theslmplifled hydraulic Operating cll'cuit employing reservoir 20. Also,when fluid is supplied to the a 223 1 gl a jzfi p ov a hydraulic 4oconverter 34 through both of the conduits 30 and 32, there is a dischare of fluid throu h the operating circuit fora hydraulic motor employingconduit 35 to exhaust gdischarge i g gfig ggiz fgg i gg whwh the valvmgthrough the various conduits communicating Another object of thisinvention is to provide 3 22 2 szgi g i li gg gg g $33: 3; a hydraulicoperating circuit for a reciprocable d s t M ram in which the usualsurge and pre-fill valves nven y mo or are eliminated through a novelarangement of a The valve f' 28 15 arranged m the valve fluid pressureconvert. 26 to connect either of the conduits 30 or 32 with circuithaving therein a fluid pressure convertor 3 th r hil interruptm th lrmun cation with the conduit 24.

Communicating with the valve 26 is still another conduit 38 which leadsto the advancing means It for the ram 12. The conduit 38 is positionedin the valve 26 between the conduits 30 and 32 and is always incommunication with either one or the other or both thereof.

The valve member 23 is normally maintained in its centered, or Figure 1,position by means of the centering springs indicated at 40 and which maybe of any suitable design. For shifting the valve member 28 in eitherdirection from its centered position there are provided the pilotconduits 42 and 44 leading to opposite ends of the valve 26 and havingtheir other ends connected with the service ports of a pilot valve 46.The pilot valve 46 also has a pressure inlet connected by conduit 48with the discharge side of the I8 is operating, that both of thesolenoids SI and S2 are de-energized, and the ram I2 is in itsretracted, or Figure 1, position.

To commence a working stroke of the ram I2 the operator closes theswitch 68 thereby energizing the contactor .coil 'A. Energization of Awill close'the blade AI thereof to provide a holdpump I8 and exhaustports connected by the' conduit 50 with the reservoir 26. Within thepilot valve 46 is a valve member 52 which is normally held in itscentered, or Figure'l, position by the centering springs S4. In itscentered position, the valve member 52 connects both of the pilotconduits 42 and 44 with the pressure 1 conduit 48. Whereupon thecentering means 46 of the valve 26 will hold the valve member 28 in itscentered position. Upon movement leftwardly of the valve member 52 byenergization of the solenoid SI, the pilot conduit 44 is exhausted whilepressure continues in the pilot conduit 42. The valve member 28 is thusurged rightwardly from its centered position. Upon de-energization ofthe solenoid SI and energization of the solenoid S2 at the opposite endof the pilot valve 46, the pilot conduit 42 will be exhausted whilepressure fluid will be supplied to the pilot conduit 44. This will movethe valve member 28 leftwardly from its center position.

The retracting means I6 of the ram I2 is connected by a conduit 54 withone port of a valve 56 which has therein a valve member 58 normallyurged by a spring 60 into position to connect the conduit 54 with theconduit 22. Upon movement downwardly of the valve member 58 by the lever62, the conduit 54 is connected with the exhaust conduit 64. The lever62 may be moved manually or by means of a suitable cam or projectingstud assembly, not shown, carried by the ram I2 and operable uponpredetermined extension of the ram to engage the lever 62 and depressthe same.

For controlling the energization of the solenoids SI and S2 there isprovided the electrical circuit shown in Figure 2. connected between thepower lines LI and L2 the contactor coil A in series with a normallyopen start button 68. The start button is by-passed by the normally openblades AI of the contactor A and the normally closed blade B2 of thecon-' tactor B. In parallel with the coil A is the solenoid SI of thevalve 46.

Also connected between the power lines LI and L2 is a coil B which is inseries with a normally open pressure switch indicated at PS whichisby-passed by the normally open limit switch LSI and the normally openblade BI of the contactor B.

The pressure switch PS is connected with the Operation In operation, letit be assumed that the pump In Figure 2 there is r ing circuit for thecoil and also to energize the valve solenoid S I.

. Energization ofSI is efiective to move the valve member 52 of thevalve 46 leftwardly to interconnect the pressure conduit 48 with thepilot conduit 42 while simultaneously connecting the pilot conduit 44with the exhaust conduit 50. The supply of pressure fluid in the conduit42 moves the valve member 28 toward its right end position andinterconnects the pressure conduit 24 with the conduit 30 leading intothe intensifier 3'4 and also interconnects th conduit 32 leading fromthe said intensifier with the conduit 38 leading to the ram advancingmeans I4.

With the valve members 28 and 52 in the aforementioned positions, thesupply of fluid from the pump I8 is through the conduits 22 and 24, thevalve 26 and conduit 36 to the converter 34. From the converter 34 areduced pressure supply of fluid at increased volume is directed throughthe conduit 32 and valve 26 to the conduit 38. This supply of fluid actson the ram advancing means I4 to move the ram I2 toward the right.During the rightward movement of the ram I2 the fluid expelled from theram retracting means I6 is conducted through the conduit 54 and valve 56to the conduit 22 where it adds to the pump discharge and augments theadvancing speed of the said ram.

After the ram I2 has advanced toward the right a predetermined distancethe cam I0 engages the limit switch LSI, or the pressure switch PS isactuated by pressure from the advancing means I4 thereby to energize thecontactor B.

Energization of B closes the blade BI thereof to establish a holdingcircuit for the coil B and to energize the valve solenoid S2.Energization of B also opens the blade B2 thereof and deenergizes thecoil A which permits the blade AI thereof to open and to de-energize thevalve solenoidSI.

With the solenoid S2 energized and the solenoid SI de-energized, thepilot conduit 42 is connected with exhaust while the pilot conduit 44 isconnected with the pressure conduit 48. This brings about movement ofthe valve member 26 toward its left hand position which interconnectsthe conduits 30 and 38 and the conduits 24 and 32.

The supply of fluid from the pump I8 is now directed to the converter 34through the conduit 32 and a reduced volume increased pressure supply offluid is delivered from the convertor 34 to the conduit 36 and thencethrough the valve 26 and conduit 38 to the ram advancing means I4.

The ram I2 now continues at reduced speed but under increased pressure.Should it be desired to develop a greater working thrust on the ram I2,the valve member 58 may b shifted downwardly. Actuation of the valvemember 58 downwardly will operate to exhaust the ram retracting meansI6.

' After the work to be done by the ram I2 has springs S4. As mentionedbefore, this places both ,ofthepilot conduits 42 and 44 under. pressureand permits the centering means at of the valve member 2-8 to move thesaid valve member to its center position. The conduit 38 is thusconnected with both of the conduits 30 and 32 while the conduit 24 isclosed off at its valve end. In order to retract the ram l2 the valve 56is returned to its original position, if it has been moved therefrom, tointerconnect the conduits '22 and 54, thus bringing about a supply ofpressure fluid from the pump IE to the ram retracting means Hi. Thissupply of fluid urges the ram I2 leftwardly and develops a pressure inthe ram advancing means I4 which is effective to pass fluid through theconduit 38, the conduits 3B and 32, and the convertor 34 to the conduit36. The retracting movement of the ram i2 will continue until it bottomsin the cylinder ID, or until the start button 68 is again closed.

It will be noted that the circuit of this invention provides for a fastapproach of the ram 12 and for two selectively available feed rates.

It will also be noted that the fast approach of the ram is obtainedwithout the use of auxiliary booster rams and without pre-fill, surge,or unloading valves.

By employing the convertor 34 very high pressures can be developed inthe ram advancing means l4 whereby high working thrusts may be exertedby a relatively small ram. By reversing the convertor in the circuit, asupply of fluid may be directed to the advancing means M which issufficiently augmented to produce approach speeds comparable to thesewhich wouid be obtained by an auxiliary booster ram.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and conditions and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall within the scope of the appended claims.

I claim:

1. The combination with a fluid operable motor having a fluidpressure-receiving advancing area; of a fluid displacement pump; fluidpressureconverting means having first and second fluid inlet ports andan exhaust port and operable upon the introduction of fluid underpressure into the first inlet port to discharge fluid through the secondinlet port at increased pressure and reduced volume, and upon theintroduction of fluid under pressure Within the second inlet port todischarge fluid through the first inlet port at decreased pressure andincreased volume, said converting means being further operable inresponse to the simultaneous introduction of fluid under pressure withinboth of said inlet ports to discharge fluid through the exhaust portthereof; and valve means connected with the advancin area of said motor,said pump, and the inlet ports of said converting means and operable toselectively introduce fluid sent forth under pressure by said pump toeither the first or second inlet ports of said converting means whileconnecting the opposite inlet port with the advancing area of saidmotor, or to connect both the first and second inlet ports of saidconnecting means with the advancing area of said motor.

2. The combination with a fluid-operable motor having advancing andretracting areas; of a fluid pressure source; a fluid pressure converterhaving a plurality of fluid transmission ports to receive and dischargefluid to and from convertor and a fluid outlet for exhausting fluid fromsaid convertor, said convertor being operableupon the introduction offluid under pressure to one of its transmission ports to discharge fluidfrom another of its transmission ports at increased pressure and reducedvolume and upon the introduction of fluid under pressure to itslast-named transmission port to discharge fluid from its firstnamedtransmission port at decreased pressure and increased volume, saidconvertor being further operable upon the introduction of fluid underpressure to both of its transmission ports to exhaust such fluid throughits fluid outlet; a first valve means selectively operable to connectsaid fluid pressure source with either of the transmission ports of saidconvertor while connecting the other of its transmission ports with theadvancing area of said motor, or to connect both of the transmissionports of said convertor simultaneously with the advancing area of saidmotor, and a second valve means selectively operable to connect theretracting area of said motor with said fluid pressure source or withexhaust.

3. A hydraulic control circuit for a fluid-actuated hydraulic motorhaving an advancing area and a retracting area, comprising a hydraulicfluid reservoir; a fluid displacement pump conneoted with said reservoirand operable to pump fluid under pressure therefrom; a fluid pressureand volume convertor having a reduced pressure increased volume outletport, an increased pressure reduced volume outlet port, and an exhaustoutlet communicating with said reservoir; a first valve havingconnections to said pump, the reduced pressure outlet port of saidconvertor, the increased pressure outlet port of said convertor, and theadvancing area of the hydraulic motor, said first valve being operableto selectively connect either the increased pressure outlet port or thereduced pressure outlet port of said convertor with the advancing areaof the motor while connecting said pump with the opposite outlet port,or to simultaneously connect both the reduced pressure port and theincreased pressure port of the convertor with the advancing area of themotor, said convertor being operable in response to fluid pressure atboth the reduced pressure and increased pressure ports thereof toexhaust fluid through the exhaust outlet thereof; and a second valvehaving connection with the retracting area of the motor, said reservoir,and said pump, said second valve being selectively operable to connectthe retracting area of the motor with said reservoir or with said pump.

4. In a control circuit for a double-acting hydraulic ram havingram-advancing means and ram-retracting means, a fluid displacement pump,a fluid pressure convertor having a first transmission port, a secondtransmission port, and an exhaust port, said convertor being operable toreceive fluid under pressure at said first transmission port anddischarge the same at increased pressure from said second transmissionport, or to receive fluid at said second transmission port and dischargethe same at reduced pressure from said first transmission port, or toreceive fluid simultaneously at both transmission ports and dischargethe same through said exhaust port; and a valve connected respectivelywith the advancing means of the ram, said pump, and the first and secondtransmission ports of said convertor, said valve having a control membermovable to a first position connecting said pump with the firsttransmission port of said convertor while connecting the advancing meansof the ram with the second transmission port of said convertor, a.

second position connecting said pump with the second transmission portof said converter while REFERENCES CITED connecting the advancing meansof the ram with The following efe e ces are of record in the the firsttransmission port of said convertor, and file of this P t a, thirdposition connecting both the first and 5 UNITED STATES PATENTS secondtransmission ports of said converter with Number Name Dat me advancmgmeans of the 2,142,628 Banert Jam 3, 1939 2,243,978 Reader June 3,1941

HOWARD PURCELL' 2,296,647 McCormick Sept. 22, 1942 2,336,446 Tucker Dec.7,1943

